Ring manufacture,productive of line contact seal

ABSTRACT

METHODS, APPARATUS, AND IMPROVED STRUCTURE HAVING AS THEIR COMMON BASIS THE SEQUENCE OF COLLAPSING A PISTON RING IN A FIXTURE APPROXIMATING ENGINE BORE DIAMETER, AND LAPPING A LOCALITY AT THE SIDE OF THE RING WHILE SO COLLAPSED, UNTIL A CIRCUMFERENTIALLY CONTINUOUS PORTION-NARROW IN WIDTH AND PREFERABLY LINE SIZE-OF THE SIDE IS FLAT IN THE RNGE OF AT LEAST ABOUT 10 TO 5 LIGHT BANDS. THE BROADEST METHOD DISCLOSED IS THE USE EXCLUSIVELY OF RINGS SO SELECTED THAT THE INNER PERIPHERAL EDGE AT THE SIDE HAS ALL POINTS THEREON IN   COPLANARILITY TO A DEGREE EQUIVALENT TO THE STATED RANGE TO SEAL IN ABSOLUTE LINE CONTACT.

United States Patent [72] Inventor Norman M. Packard 3,337,938 8/1967Prasse 29/l56.6

A l N FOREIGN PATENTS 21] p o. Sept 6, 1968 140,799 7/1949 Australia277/216 [45] Patented June 28, 1971 Primary Examiner-John F. Campbell I73 Assignee international Harvester Company. Assistant Examiner-VictorA. DiPalma Chicago. 111. Attorney-Noel G. Artman [54] RING MANUFACTURE,PRODUCTIVE F LINE CONTACT SEAL 11 Drawing Figs ABSTRACT: Methods,apparatus, and improved structure U58 having as (heir common the equenceof colla in a 51/290, 277/216 piston ring in a fixture approximatingengine bore diameter, I In! and a locality at the side of the ring oolla ed [50] Field of Search 29/l56.6, um a i f ti l, continuous portinna"ow in width 156'63; 73/1 120; 277/216. 1031;/29'3- 324 and preferablyline size-of the side is flat in the range of at [56] Rehnnces Citedleast about to 5 light bands. The broadest method disclosed is the useexclusively of rings so selected that the inner UNITED STATES PATENTSperipheral edge at the side has all points thereon in coplanari-2,177,700 10/1939 Fisher 277/216 ty to a degree equivalent to the statedrange to seal in absolute 3,073,689 1/1963 Kupfert et al 51/324 linecontact.

RING MANUFACTURE, PRODUCTIVE UF LINE CONTACT SEAL Blowby presents aproblem in production piston engines. The need, as l envision it, is tocontrol blowby so that in production we are capable both of making itpredictable and of keeping it at a uniform, desirably low value fromengine to engine, at least in precision made production engines which,in general, are of the multicylinder type. Blowby is one of the factorsaffecting lubricating oil control. Solving the blowby problem will havea material influence on reducing oil consumption in engines, and l havediscovered that the key to the solution is in the compression rings onthe pistons.

According to my inventions, the engines are sealed, i.e., each pistonand its surrounding cylinder wall are mutually sealed by an interposedpiston ring either so selected that the inner peripheral edge of thering at the groove sealing side thereof is coplanar at all points orelse so localizedly lapped, in a narrow band along the inner peripheraledge at the side, that the ring will seal the confronting side of areceiving groove in a narrow, circumferentially continuous ring ofpressure contact which amounts to line contact or, at most, has onlyslight width at the widest points. The resulting ring at the side of thepiston ring makes up only a minor portion of the overall side. Theoverall side of the ring which seals the groove side as aforesaid forms,for at least its major portion as viewed in cross section, a slightangle to the groove side and is frustoconical although the groove sidemay or may not be frustoconical.

The disparity in the angularity between the mutually confronting sealedand sealing sides of the respective receiving groove and piston ring isdeliberate, and under pressure during compression and firing in theengine cylinder the ring deflects into what amounts to face contact withthe groove side over at least a major portion of the side of the ring,thus multiplying to substantial proportions the sealing area at thecritical time. So sealing with narrow band contact and line contact orsealing with face contact, depending upon the presence or absence ofhigh pressure conditions, complement one another to reduce the blowby,i.e., escape of firing pressure into the crankcase by leakage in thecylinders past the pistons.

My inventions thus materially reduce or substantially eliminate theproblem of unpredictability and largely uncontrollably high magnitude ofblowby, as will now be explained in detail. Features, objects, andadvantages will either be specifically pointed out or become apparentwhen, for a better understanding of the inventions, reference is made tothe following description taken in conjunction with the accompanyingdrawings which show certain preferred embodiments thereof and in which:

FIG. 1 is a longitudinal elevational view of a portion of a piston andcylinder in an engine embodying the present ring invention, and shownwith the embodiment in one of its operating positions in collapsedstate;

FIG. 2 is an enlarged fragmentary view corresponding to FIG. I, butshowing that embodiment of the invention in another operating position;

FIG. 3 shows the embodiment of FIG. I in the same collapsed state, butin a lapping fixture for doing the work on the ring to bring it to thefinished stage;

FIGS. 4, 5, and 6 are sequence views of the ring as lapped, showing therespective beginning, intermediate, and finished sta es;

I IG. 7 corresponds to FIG. 2, insofar as a fully seated or firingposition is being viewed, but showing a modified piston and ringstructure;

FIGS. 8 and 9 are similar to FIGS. 1 and 2, insofar as respective lineseated and fully seated positions are being viewed, but showing afurther modified piston and ring structure;

FIG. 10 corresponds to FIG. 8, but with the ring in a lapping fixture tobring it to the final stage; and

FIG. I1 corresponds to FIG. I, insofar as a line seating position isbeing viewed, but showing a further modification of the ring.

My inventions about to be particularly described apply to, among others,rectangular positive torsion ring structure, keystone rings with eitherplain structure or positive torsion structure, and rectangular negativetorsion or reverse dish ring structure. Slightly oversimplified, apositive torsion ring is basically one which is twisted in a ring grooveof rectangular cross section with the lower side of the ring bearingagainst the bottom of the groove at the radially inner part of thegroove and inclining upwardly and outwardly therefrom. A positivetorsion keystone ring is, to a much more moderate extent, along the samelines above but it tits in a tapered or wedgeshaped groove on a piston.A keystone ring without torsion causing it to twist in the groove is aplain keystone ring, but it nevertheless tits in a wedge-shaped groove.Finally, the negative torsion ring twists in a rectangular groovewhereby what the ring does is to have the upper side of the ring bearagainst the top of the ring groove in the inner part of the groove,slanting downwardly and outwardly therefrom, or else what the ring doesis to have the lower side of the ring bear against the bottom of thering groove in the outer part of the groove, inclining upwardly andinwardly therefrom, or else 'the ring does both.

All of the rings concerned are the so-called split rings, having aparting located at some point around the circular length of the ring.Each such ring is compressed from its normal relaxed or free state bymeans of a ring compressor so that it assumes a collapsed state with theparting closed or substantially so. In reaching the collapsed state, thetorsion ring twists or distorts or dishes out of its normal plane inwell-known way dependent upon whether the curved inner face at the backof the ring has been selectively undercut at one side or the other ofthe ring. When collapsing, the torsion ring always takes a dishedposition with the undercut portion occupying what becomes the concaveside of the dish.

The metal of the foregoing rings is usually cast iron, and the pistonsare cast iron or an aluminum alloy. Pistons in the latter category havethe compression ring grooves formed either directly in the aluminum orin hardened, grooved inserts carried by the aluminum piston.

Against this background, it is believed that FIGS. 1, 2, 3, 4, 5, and 6,showing one preferred embodiment of my ring invention, can be readilyunderstood.

LINE SEATED OPERATION, COLLAPSED STATE-FIG. l

A rectangular, positive torsion ring 20 is shown in that one of itsoperating positions in an engine in which the ring is line seated at theside, Le, a narrow seal band 22 thereon establishes at least linecontact with the inner portion of the confronting lower side 24 of arectangular groove 26 in a piston 22%. The piston reciprocates withinthe wall 30 of a cylinder of a multicylinder engine 32, being sealed tothe wall by the ring Ztl. The ring 20 is a compression ring, and isillustrated in the top or first ring position on the piston although thedesign is fully effective as the second, third, etc., compression ringon a multiringed piston.

The adjacent ends of the ring defining the parting indicated at 341 arepractically touching at the operating temperature of the ring, but ineach engine the designer always takes care to keep them from actuallybottoming against one another because of the danger that the ring mightseize in the cylinder. The ring is thus a live ring, functioning at alltimes as a cast iron spring.

In the collapsed operating state in the groove as shown in FIG. I thering has a twisted position, due to its inherent torsion, during thesuccessive exhaust and suction strokes of the piston 26. The slightacute face angle, which the essentially cylindrical face 36 of the ringmakes with the vertical, accounts for a unidirectional oil pumpingaction produced by the ring. During the exhaust strokes referred to eachof which is in the outward (upward) direction, the ring provides goodoil control, keeping an oil film on the hone pattern in the wall 30 at asufficient but minimum thickness for lubrication purposes. During eachsuction stroke, which is inward, the ring 20 due to its slight faceangle scrapes the oil in the inward (downward) direction because of theclosed pocket formed by the contact between the ring and each of thecylinder wall 30 and the lower groove side 24. The oil cannot readilyget into the groove 26 because of the ring of pressure contact of thesealing band 22, and so the oil is pushed inwardly ahead of the bottomside of the ring indicated at 38 and now to be described in connectionwith the operating conditions of compression and firing.

FULLY SEATED OPERATION, COLLAPSED STATE-FlG. 2

During the successive compression and firing strokes of the piston 28,the ring of pressure contact effected by the line seated seal band 22always insures as a first stage of sealing that no appreciable pressuredissipation can take place by leakage past the ring. Hence, the ring 20is flattened by the ensuing buildup of pressure and, by a second stageof sealing, the bottom side 38 of the ring is forced into a fully seatedarea of face contact against the major portion of the confronting bottomside 24 of the groove 26.

The trapped pressure produces a consequent downward and outward forceagainst the respective flat upper side 40 and curved rear side 42 at theback of the ring. Hence, the curved face 36 at its lower edge is bothspring loaded mechanically and pressure loaded by gas into essentiallyleak-free contact with the cylinder wall 30.

Although not present to to the exaggerated extent as shown in FIG. 2,there is in fact an obtuse angle of intersection between the band 22 andthe major portion of the lower side 38. The respective lower and uppersides 33 and 40 are parallel, horizontal, and fiat both in this facecontact collapsed state for obvious reasons and in the state now to bedescribed.

NORMAL RELAXED OR FREE STATE-FIG. 3

In the free spring state of the ring having a fully expanded diameter asshown by the broken lines 20a in FIG. 3, the adjacent ends of the ringmove to their fully withdrawn position so that they are partedconsiderably at 34. it is when the spring is unloaded and in free state,during the manufacturing process, that the respective upper and lowersides 40 and 38 are made fiat and parallel, and the side 38 ispreferably lapped in a lapping fixture to within the range of to 5 lightbands or to greater flatness, such as to 2 light bands flat. Hence, thebottom side 38 of the ring will provide effective face sealing when inthe fully seated operating position shown in FIG. 2.

In order to make the ring twist because of its cross section, the curvedrear side or back 42 is relieved by an undercut adjacent the top side 40only, as by a chamfer or, as actually illustrated, a counterbore 44. Sothere is definite asymmetry in the cross section whereby, when theparting in the ring is closed, the ring dishes into an upwardly concavecollapsed form, now to be further discussed.

LAPPING, BEGINNING STAGE-FIG. 3

An aspect of novelty is believed to reside in the fact that, prior to mydiscovery of the realities of the matter, there had been and never wasany basis for accepting as a foregone conclusion that a positive torsionring, flat on the bottom side in free state, would so uniformly distortinto its collapsed state as to establish line contact with a groove sidewhich was to be sealed thereby and which was planar or substantially so.Prior to my discovery, and consistently confirmed as a fact in randomchecks made by me, it was never appreciated and yet as a general rulethe usual production-made positive torsion ring in collapsed state wasnoncoplanar along its sealing inner periphery which presented asuccession of high spots and low spots, somewhat according to a wavy orundulating pattern. Hence, there existed no fundamentally orderly andsystematic way whereby the engine designer or assembler could predictthe amount of blowby which would be produced by each engine when finallybuilt.

One of my methods of providing a piston ring in production engineseffective to control the blowby and oil consumption to an exceptionalproportion by better sealing includes, as a first step, compressing aring, such as the ring 20 in FIG. 3, radialwise into its collapsed statein the movable fixture 46 of a lapping apparatus. The ring receivingmouth 48 of the fixture has identical diameter to the cylinder bore sizeofthe engine in which the ring 20 is to be installed. The lappingapparatus further includes a flat, fixed confronting lapping surface 50,the ring 20 being held relative thereto so that the side 38 forms at alltimes a slight acute angle to the flat surface 50. The mouth 48 of thefixture 46 is, on the one hand, shallow enough that the inner peripheryonly of the lower side 38 of the ring projects into contact with thesurface 50. At the same time, the shallow mouth 48 is nevertheless deepenough to engage the outer periphery of the side 38, where the latterjoins with the face 36 of the ring, thereby retaining the ring in acollapsed state the same as if restrained in operating condition in acylinder ofthe nominal bore size ofthe engine.

in the case of the usual positive torsion piston ring prior to mydiscovery, low spots would be present on the inner periphery at the sideof the ring 20 which would not contact the surface 50 at the beginningoflapping.

LAPPING, INTERMEDIATE STAGE-FIG. 5

Lapping is preferably accomplished by forced motion of the fixture 46 ina figure eight movement in the plane of the fixture and ring relative tothe fixed surface 50. Other specific movements to produce equivalentlapping can be utilized, the critical factor being to preventperpendicularly loading the fixture 46 on the surface 50. About 1 poundtotal perpendicular pressure has been found acceptable, withoutproducing the undesirable result of distorting the ring 20 from thenormal twisted position into which it would be distorted by torsion whenoperating in a compression ring groove in an engine.

The first points abraded by the lapping compound on the flat surface 50will be the high spots 52 initially forming circumferentiallyspaced-apart flats on the inner periphery of the lower ring side 38.Continued abrading by the surface 50 keeps lowering the high spots 52relative to the plane of the lowest spots of the inner periphery.

LAPPING, FlNlSHED STAGEFIG. 6

In the stage illustrated in FIG. 6, the lapping of the ring 20 hasprogressed to the final stage, all lapping having been performed withthe parting 34 closed or substantially so although the parting isgreatly emphasized in the FIGS. ofdrawing to illustrate presence of thegap. All spots will have merged into the common continuous sealing band22 with the former high spots forming the widest portions 52a in theband. Here again, the bandwidth is greatly exaggerated to be perceptiblein the illustration. Because of its finite width dimension, the band 22can be literally said to have flatness, and such flatness is measurableand preferably in the range of at least about 10 to 5 light bands. N0greater approach has been found necessary to perfect flatness of theseal band in order to achieve [ll'Z practical control of blowby desired,although 2 light bands would, for example, improve the operation atleast theoretically.

Anyway, the precise range of flatness is not the matter of basicimportance here involved, but rather it is systematic analysis andinsurance in all cases of a good sealing contact. So a band of theflatness and specific shape of the varied width band 22 as shown in FIG.6 is not necessarily the most desirable, nor is the provision of a banddesirable in all cases.

BAND CONTACT, NARROW WlDTH Achieving sealing contact by what is believeda better way than the foregoing is by the provision of a ring having aband of essentially uniform narrow width, not illustrated.

Since my discovery, it has been observed that at times positive torsionrings produced in manufacture include some rings which, by happenstance,have a protruding inner periphery which in the collapsed state of thering is practically coplanar at all points. Despite their randomoccurrence, the marshalling out of such rings by a selection-rejectionprocess is feasible, and each of those rings in such a select group islapped only slightly whereupon the group will have fully advanced to thefinished stage. lnherently, such rings have a very narrow sealing band,almost uniform in width, and they highly successfully seal in accordancewith the principles of my inventions.

LINE CONTACT-FIG. 4

Perhaps the best way, and no doubt the ideal way, of accomplishing thesealing hereof is to apply the selection-rejection process and separateout all rings in a production run which by happenstance display precisecoplanarity of the inner periphery at all points when the ring isdistorted into the collapsed state.

In fact since my discovery, it has been observed that careful control inring manufacture over such variables as metallurgy, manufacturingprocedure, and details of ring design such as cross section and thelike, can materially increase the proportion of rings in a productionrun above what could be expected as the happenstance or random grouphaving coplanarity of the inner periphery of the bottom side at allpoints. So through careful control of the manufacturing process andother variables, the deliberate increasing of the proportions of suchrings in a run can be realized to an expectancy of 50 percent andbetter, perhaps upwards of 90 percent, or 95 percent, or possibly of 98percent, which will have what can be stated as the coplanarity inherencyin the peripheral portion of the ring when distorted into collapsedstate. Stated another way, the inner periphery of the sealing side ofthe ring in each case is a uniplanar knife edge.

In such case, the product becomes not the happenstance or exception butthe rule, and what essentially amounts to absolute line contact ofsealing, i.e., contact having only a substantially continuous lengthdimension and no width, can be achieved with the ring. To tell thetruth, the confronting side of the groove which is sealed by such a ringin service actually acts as a lapping surface to a degree, and in thecourse of engine operation the groove side can lap the ring peripheryfrom an edge into a band.

Obviously, the selection-rejection process will have to be retained atleast to the extent of a spot check. Though possible, it sounds somewhatidealistic to expect to achieve rings which to a I00 percent extent haveinner peripheries on each of which the locus of all points will fall inone plane. Practical manufacturing does not allow absolutepredictability and certainly the manufacture of positive torsion ringswhich must be distorted to install them does not allow absolutepredictability.

The ring of FIG. 4 can be viewed as such a ring having substantiallyabsolute coplanarity along the inner periphery, and it will beunderstood that the parting at 34 although greatly exaggeratedcorresponds to the operative parting or split or gap in the ring incollapsed state in the line seated position. The spot checking, referredto, of such production rings is no destructive test, and a ring sotested is merely lapped a few test strokes to the point where theresulting uninterrupted flat band can be perceived visually. The ring isperfectly usable, establishing in the line seated position a bandcontact and not literally line contact with the confronting surface tobe sealed.

FULLY SEATED, POSITIVE TORSION KEYSTONE RlNG--FlG. 7

In the modification of FIG. 7, the parts are the same except that a ring60 as shown is a positive torsion keystone ring and the receiving groove62 therefor is a complementary wedgeshaped groove having a taper.Similarly to the preceding embodiment, the back of the ring 60 isundercut at 64 with a counterbore in the upper part of the curved innerside of the ring. The ring 60 has a bottom side 66 provided with alapped seal band 68 located at the inner periphery where the bottom sidejoins with the back of the ring.

The ring 60 is not shown in its line seated operating position whichoccurs in the collapsed state and which can be readily visualized.Instead, FIG. 7 shows the ring in its fully seated position in collapsedstate providing a wide area of face sealing contact with the confrontingbottom side 70 of the receiving groove 62.

Consistent with the usual design of keystone rings, the ring 60 has abarrel face 72 which as viewed in cross section affords a smoothcurvature making contact with a confronting cylinder wall 74 as the ring60 changes between line seated and fully seated positions in the groove.

The operation is the same as in the preceding embodiment, during boththe consecutive exhaust and intake strokes of the engine on the one hand(line seated), and the consecutive compression and firing strokes of theengine on the other hand (fully seated).

In customary manner, the bottom side 66 of the ring 60 in collapsedstate in the line seated position (not shown) makes a slight angle tothe horizontal, whereas the groove side 70 is machined with a slightangle to the horizontal which is nevertheless somewhat larger than thereferred to angle of the ring side 66. Hence, the ring 60 reacts inoperation by fully seating against the groove side 70 under compressionand firing pressures in the engine.

Most torsion type rings are of rectangular shape, which rings usuallyhave the greater susceptibility to ring sticking because of the shape.Inasmuch as keystone rings are substantially free from susceptibility tosticking, most of the keystone rings are plain keystone rings.

KEYSTONE RING, PLAlN-FIGS. 8 and 9 A plain keystone ring is illustratedat in collapsed state in the respective line seated position in FIG. 8and fully seated position in FIG. 9. During exhaust and intake strokes,essentially line contact according to the inventive principles hereof iseffected between a flat seal band 82 forming the inner periphery of thebottom side 84 of the ring and a confronting bottom side 86 of thewedge-shaped or tapered ring receiving groove 88. During collapse of thering 80 from its free spring condition, not shown, to the collapsed,line seated, operating position as shown in FIG. 8, no twist occursbecause no twistproviding asymmetry is present in the cross section ofthe ring 80. Only line contact results because the groove side 86 ismachined to have a slight angle to the horizontal which is somewhatgreater than the slight angle which the ring side 84 makes with thehorizontal.

Both the compression pressure-and the firing pressure in the enginecause the ring side 84 to fully seat in face contact against the bottomside 86 of the groove, as shown in FIG. 9.

PLAIN KEYSTONE, LAPPlNG-FIG. 10

For purposes of lapping the keystone ring 80 is, with no attendant twistbecause of lack of torsion from asymmetry, collapsed from the freespring state indicated by the broken lines 800 to the line contactposition in collapsed state as shown by the solid lines 80 in FIG. 10. Alapping fixture s2 therefor has an open mouth 94 holding the ring incollapsed state with the inside and outside diameters of the respectivemouth and ring equal to the cylinder bore size of the engine for whichthe ring is designed. The inner periphery only of the bottom side 84projects into contact with a fixed confronting lapping surface 96.

The lapping surface 96 is convex, being for example, frustoconical or,as actually illustrated, frustospherical The ring 80 is maintained in aconsistent attitude relative to the surface 96 so as to have the bottomside 84 form the same slight angle thereto at all times. Figure eightlapping movement or other suitable motion of the fixture 92 relative tothe fixed lapping surface 96 abrades away the high spots and shapes theinner periphery of the side 84 into a seal band 82 which can lie along agroove side in a continuous line.

The shallow mouth 94 is shallow enough not to interfere with the surface96 and yet is at the same time deep enough to insure that the ring 80 isfirmly retained in collapsed state.

The groove for the keystone ring is, in contrast to the grooves for theother rings herein described, never narrow enough so that the ringsimultaneously touches the upper and lower groove sides. Hence, thekeystone ring when within a comparatively wide groove, as well as theother rings when within similarly appropriately wide receiving grooves,are forced into the line seated operating position against the bottomside of the groove only on the exhaust stroke. Nevertheless the lineseated position offers help which is ofa critical nature duringcompression and firing, but offers no help at all during suction when,in point of fact, the ring is drawn up against the upper side of thegroove. During compression and firing as just referred to, the lineseated position is critical for sealing at the first stage in orderthat, as the second stage, the rising pressure can accumulate and causefull seating of the ring in face contact with the lower side of thegroove.

ln torsion rings, simultaneous engagement between the ring and bothsides of the groove (i.e., the groove is comparatively narrow in thesense just referred to) is, desirable when the amount of ring twist isto be limited by engagement of the ring with both sides of the groove.Simultaneous engagement is also desirable for other reasons and, if notessential, is especially desirable with certain rings. For example, somenegative torsion rings can display a deficiency both during exhaust andalso during compression and firing by its failure to establish properline seated position because of the inherent geometric incompatibilitybetween the nonconcentric frustoconical bottom ring side and thecircular outer edge of the groove bottom side.

My inventions aid in overcoming such deficiency in the negative torsionspring embodiment now to be described.

NEGATIVE TORSION OR REVERSE DlSH RlNG-FlG. 11

A negative torsion compression ring 100 is illustrated in FIG. 11. Thecross section causes the ring, when collapsing, to twist or distort fromits normal relaxed or free spring state into the parting closed statewhereby the lower side 102 of the ring in contacting the rectangularreceiving groove will bear against the outer part of the lower grooveside 104, inclining upwardly and inwardly therefrom. The upper side [06of the ring in simultaneously contacting the receiving groove will bearagainst the inner part of the upper groove side 108, pressingthereagainst with a narrow seal band 112 at the ring side periphery andinclining downwardly and outwardly therefrom.

The negative torsion ring 100, by reason of the undercut 114 thereofbeing located in the back of the ring adjacent the lower side I02,dishes convexly upwardly and serves primarily as a compression ring,preferably, as the second, third, etc., compression ring below the firstor top compression ring, not shown.

Notwithstanding the fact that the lower side 102 of the ringtheoretically seals the lower groove side 104 to prevent any oilentering the ring groove, the slight frustoconicity of the side 102 atleast in theory will not firmly seat along the circular confrontingportion of the groove side I04 for the reasons given, except when thetwo are geometrically concentric.

However, the planar band 112 and the confronting planar upper grooveside 108 establish at least line contact in all radially shifiedpositions and therefore prevent passage of oil in or out of the groove.Specifically, close line contact of the band 112 during inward strokesof suction cause line seated sealing. Close line contact of the band 112as the first stage during compression and firing, insuring properpressure rise for the second stage of full seating of the ring, isessential to establishment of the face contact of full seating. Also,line contact of the band 112 which is enforced by the comparativelynarrow rectangular groove during exhaust causes line seated sealing.

The negative torsion ring is not illustrated in collapsed state in thefully seated operating position, which can be readily visualized as thestage beyond the point of occupying the position actually illustrated,i.e., the face contact stage beyond the point when the ring 100 is incollapsed state in the line seated operating position illustrated.

The general utility of my inventions as they apply to various rings isbelieved covered with adequate and representative examples hcreinabove.In the interest of brevity, the specific utility of my inventions is nowset out only with respect to the literal line contact modification ofwhich FIG. 4 is illustrative and the narrow band contact modification ofwhich FIG. 6 is illustrative, all as embodied in a positive torsion,rectangular ring. The advantage of positive torsion, despite the ringbeing fitted in a rectangular groove and hence being susceptible tosticking, is that the ring has an operatively built-in freedom oftwisting motion tending to prevent buildup of carbon in the ring groovewhich, in accumulated quantities therein, can cause ring sticking. Theeffective sealing accomplished hereby insures twisting under theperiodically trapped pressures, making the rectangular cross-sectionalring to become entirely practicable. The designer can realize definitecost savings by avoiding turning to a keystone shape, which shape makesfor a much more expensive ring due to the inside cone angularity of themajor sides which must be worked upon during manufacture of the keystonering.

There are two sure ways of taking advantage of my inventions to the lastdegree. The way, in the case of the foregoing rings or equivalents whichaccomplish effective line seating not literally so but actually by bandseating, is to accurately lap a narrow seal band on the inner peripheryof the seating side of every ring. The way, in the case of the foregoingrings and equivalents which accomplish line seating substantiallyliterally, i.e., the sealing side of the ring has frustoconicity withthe inner periphery of the side protruding and being substantiallycoplanar at all points on the periphery so as to have practically nowidth dimension, is with enforced selection-rejection by a 100 percentinspection process of all rings whereby any seal ring having aprotruding inner periphery in which all points are not coplanar alongthe periphery is discarded.

At all events, the rings in both cases are used in the same way inengine manufacture, e.g., in the manufacturing process of an engineprovided with a number of cylinders and with that number of ring groovedpistons individual to the respective cylinders. The process comprisessealing the pistons with the compression rings by installation of such aring in each compression ring groove with an associated side of thegroove confronting one sealing side of the ring; and construction ofsuch engines by assembling individual pistons in the respectivecylinders with each ring engaging a cylinder wall at all times to retainthe ring in collapsed state on the piston, and with the ring effectiveduring engine operation such as exhaust or suction to establish asubstantially continuous pressure ring of at least line contact betweenthe protruding inner periphery of the frustoconical one sealing side andits associated confronting groove side to seal the piston, and duringengine operation such as compression or firing to establish asubstantially continuous pressure ring of full seated contact betweenthe major portion of the frustoconical one side and its associatedconfronting groove side to seal the piston.

Engines so manufactured meet the desiderata of controlled blowby, and ofcontrolled oil consumption to the degree that would be affected byblowby. That is to say, with low blowby being predictable it followsthat oil consumption will be predictably low, in absence of inordinateconditions that might cause the engine to use excessive amounts oflubricating oil.

Broadly, the basic system here involved is to change from the casehitherto of having a good seal between ring side and groove side solelyas the exception or happenstance, and instead to make it the generalrule that the ring side and groove side have a substantially continuousring of pressure contact when the ring is line seated or equivalent(i.e., narrow band seated) and when the ring is fully seated against theside of the groove. Not only is gas leakage avoided in excessive amountssuch as might partially or altogether prevent a torsion ring fromtwisting, but also leakage at the ring is kept within minimum controlledlimits.

As a practical matter, all of the smooth surfaces hereinabove discussedare either substantially flat or substantially cylindrical. Hence, theangularities are admittedly exaggerated in the drawings, particularly inthe case of the face angle of the face 36, FIG. 2 which, in itspractical range of about 1 or 2 or 3 from the vertical would at somepoint be hardly perceptible at all, and also in the case of the bottomside 26, FIG. I, which is not much greater than the just stated 1 or 2or 3 in angularity from the horizontal.

Variations within the spirit and scope of the inventions described areequally comprehended by the foregoing description.

lclaim: 1. Method of providing a piston ring in production engineswhich, at least when the ring is in a collapsed state conforming to acylinder bore size for which the ring is nominally designed, becomesclosed or substantially so, and which presents at least one side of thering which is generally frustoconical, comprising the steps of:

compression of the ring radialwise into its collapsed state;juxtaposition of a confronting lapping surface of a shape and attitudecausing localized lapping whereby the inner periphery only of said sideof the ring projects into local contact with the confronting lappingsurface, so that said side forms at all times a slight angle to saidsurface;

production of relative motion between the ring and confronting lappingsurface, providing the side with a substantially continuous lappednarrow seal band at said locally contacting inner periphery; and

introduction of said ring in an engine in collapsed state between thecylinder wall and a piston, arranged in a piston ring groove with thecylinder wall engaging the ring to retain the latter at all times incollapsed state on the piston, and with the ring effective during engineoperation to establish a substantially continuous ring of pressurecontact between the narrow seal band at said side of the ring and theside of the groove at that side.

2. The invention of claim 1, characterized by the introduced ring beingarranged in a rectangular piston ring groove;

the operation of the ring in collapsed state in said enginecharacterized by twisting the ring in the rectangular groove withtorsion during engine suction and exhaust so as to render said side ofthe ring frustoconical, and flattening the ring in the rectangulargroove with pressure during compression and engine firing.

3. The invention of claim 1, characterized by the confronting lappingsurface being flat, the relative motion being movement of the ring inthe plane of the ring.

4. The invention of claim 3, further characterized by the relativemotion being figure eight movement.

5. The invention of claim 1, characterized by the confronting lappingsurface being a generally convex surface;

the relative motion being movement of the ring on, and

while maintaining contact with, said convex surface.

6. In a method of providing a piston ring for production engines which,when the ring is in a collapsed state conforming to a cylinder bore sizefor which the ring is nominally designed, becomes closed orsubstantially so, and which presents at least one side of the ring whichis generally fnistoconical, the steps of:

compression of the ring radialwise into a state of simulation simulatingits collapsed state in the engine;

juxtaposition, against the ring in its state of simulation, of aconfronting lapping surface of a shape and attitude causing localizedlapping whereby the inner periphery only of said side of the ringprojects into local contact with the confronting lapping surface, sothat said side forms at all times a slight angle to said surface;production of relative motion between the ring and confronting lappingsurface, providing the side with a substantially continuous lappednarrow seal band at said locally contacting inner periphery; and

relief of the compression, relaxing the ring from its state ofsimulation, to free spring state with the ring relatively opened up.

7. Method of forming an internal seal side band on the inner margin of asplit piston ring, comprising:

lapping the ring against a confronting lap surface while applyingpressure to the ring which distorts the ring to maintain it closed orsubstantially closed during lapping; and

relieving said pressure, relaxing the ring whereby the resulting lappedside band on the inner margin of the ring side intersects that side in aincluded angle which is oblique.

